Industrial vibrators are utilized to enhance fluid flow of matter not prone to act like a fluid, i.e. solid matter in small particulate form such as sand, grains or any variety of small pellets stored in bulk. Often these items are kept in large containers such as hoppers or large bins where settling often causes the bulk density of the particulate matter to increase during storage, making fluid flow difficult. Vibration to the outer surface of the container by an industrial vibrator reduces the solid matter bulk density and enables fluid-like flow. Industrial vibrators are used to improve fluid flow of the particles just prior to transferring the matter by vibrating the container, or during solid matter transfer by vibrating the outer surface of a transfer line.
Two types of pneumatic industrial vibrators are commonly used to cause the vibratory action; an impact vibrator that produces vibration by a piston impacting a striking plate and an air cushion vibrator which uses a cushion of air to separate the piston from the striking plate. When impact pneumatic vibrators are used, the action of a steel piston impacting a metal striking plate can produce noise levels that violate safety and comfort levels. Noise can contribute to worker's physical ailments such as hearing impairments, headaches, fatigue and high blood pressure. Noise levels are reduced with air cushion vibrators but so is the vibratory force. Air cushion industrial vibrators often lack the force to impart vibrations required to unwedge tightly packed particles. To overcome the problem of unacceptable noise levels in impact vibrators, elastomer has been used to muffle noise. Until the present invention, however, the type of elastomer used and the method of attachment often caused disintegration of the elastomer as a result of the heat-friction from impacts occurring at the rate of up to 1500 to 5000 vibrations per minute.
McKee, U.S. Pat. No. 4,129,388 discloses a reciprocating pneumatic piston vibrator having an elastomer that prevents the piston end from directly striking the impact end of the piston chamber. McKee '388 discloses that the resilient elastomer material is adapted to be mounted between the base closed end of the cylinder and the piston end for the purpose of absorbing the noise of impact. The elastomer material may be on either impact surface, attached to the piston or the piston cylinder end. McKee '388 also discloses a piston wholly constructed of elastomer.
Blower, U.S. Pat. No. 3,917,233 discloses a pneumatic vibrator for foundry molding machines having a cylindrical striker insert fitted within a recess of an end cap. The striker insert is made of material having very low sound transmitting characteristics such as urethane, rubber or similar materials. It further discloses a striker insert made of urethane rubber having a durometer hardness around 80 to 100. This striker insert is squeezed into the recess of the end cap and may be secured in the recess by mechanical fastener means or adhesive.
Fewel, U.S. Pat. No. 4,288,165 discloses a vibratory actuator used in vibrator machines. The vibratory actuator combines the functions of a hydrodynamic journal bearing and an eccentrically weighted shaft into a single assembly. In one embodiment of this invention, the base and frame of the machine include a base supporting a frame interconnected by springs. The springs may be coil springs or elastomeric springs.
References providing general background interest consist of Lash, U.S. Pat. No. 3,731,907 which discloses a vibrator system with a sleeve member containing a tapered bore for positioning upon another tapered bore affixed to the surface that is to be vibrated, thus eliminating mounting bolts. Blakeslee et.al., U.S. Pat. No. 3,363,806 discloses a vibrator for bins or receptacles which employs a hydraulic actuating means. Blakeslee et.al. '806 also discloses a timing means for actuating the vibrator at timed intervals. Lash, U.S. Pat. No. Des. 189,793 discloses a design for a storage hopper. Konyak et. al., U.S. Pat. No. 4,067,549 disclose a ceramic rapper rod assembly for electrostatic precipitators for use in high temperature environments. Kita et. al., U.S. Pat. No. 4,083,415 disclose an impact bit for down hole operations comprising a body adapted for being chucked into an impact motor.
Prior to the present invention, the longevity of elastomers used with elastomeric-tipped pistons was limited. The elastomer often disintegrated as a result of the stress and frictional heat caused by a reciprocal steel piston impacting a metal striking plate at a rate of 1500 to 5000 times per minute. The method of attachment of the elastomer to the striking end of the piston also contributed to limited longevity of the elastomer. The known methods of attachment were not be able to withstand the stresses of rapidly repeated impacts and thereby required frequent replacements.
What is desired is a rubber or elastomer tip on the striking bottom of the piston within an industrial vibrator that reduces noise levels to acceptable decibels. It is also desired to have an elastomer with a durometer rating that enables it to withstand frictional heat and wear of 1500 to 5000 impacts per minute. Also necessary is a method of attachment of the elastomer to the piston that will not loosen upon repeated impacts.